Bill Clinton, the governor of Arkansas, became the undisputed front-runner for the Democratic president nomination with a convincing win on Tuesday in Florida, the focal point of the Democrats` Super Tuesday campaign.

President Bush, too, rolled to an easy 2-to-1 win over his challenger, Patrick Buchanan.

But Clinton`s smaller margin was the bigger news.

Clinton pulled about half the state`s votes and won by more than 15 percentage points. The margin dashed any speculation that former Sen. Paul Tsongas of Massachusetts could eke out a moral victory by finishing a close second.

With roughly five-sixths of the votes counted, Tsongas was getting about one- third of the votes; former California Gov. Jerry Brown was lagging badly, though he topped the critical 15 percent threshold to win convention delegates in three congressional districts.

The results, Clinton backers said, should erase the perception that Clinton is a regional candidate who cannot win outside the South.

``The condos in Dade, Broward and Palm Beach are Northeastern U.S.,`` said Lt. Gov. Buddy MacKay, Clinton`s state chairman. ``We know that you`ve got the Middle West on our west coast. In Orlando, you`ve got a conglomeration of everything, and North Florida is still the South.

``He won them all,`` MacKay said. ``This is kind of a pilot project on whether you can run all over America.``

For Tsongas, the defeat was a repudiation of his Super Tuesday strategy -- pouring all his resources and campaign time into Florida in hopes of pulling an upset.

Tsongas decided last week virtually to stop campaigning in the other Super Tuesday states. He counted on a victory in Massachusetts, his home state, and he all but conceded defeat in the other jewel, Texas. Clinton was also a lock to win the other Southern states that voted on Tuesday, Tsongas` staff decided.

But Florida, they thought, was winnable. So Tsongas crisscrossed Florida to pick up votes and media attention, hitting three and four cities a day. His decision made Florida the focus of Super Tuesday attention on the Democratic side.

One issue that appeared to cost Tsongas dearly: Social Security.

One section of his 80-page campaign blueprint, A Call to Economic Arms, mentioned in passing that he might eventually support a limit in annual cost- of-living Social Security increases, as part of a larger package to revitalize the nation`s economy.

It gave Clinton a powerful issue, especially in a state in which one in five residents receives Social Security. In speeches, Clinton did not raise the issue directly. But campaign literature hinted that Tsongas was not friendly to retirees, and one of the most effective mediums of all -- the condo grapevine -- kicked in.

Alice Streiker, 69, of Tamarac, voted for Clinton.

She considered Tsongas earlier, ``but there were some other things he said I didn`t go along with.`` Social Security was among them, she said.

But it was not only one issue that beat Tsongas. As returns flowed in from around Florida, they proved MacKay`s boast: Clinton won virtually everywhere.

Late Tuesday, Tsongas had won only three counties -- Alachua, Martin and Seminole. He was close in a handful of others, including Palm Beach County, which was a virtual dead heat with 80 percent of the precincts counted.

In Broward, with virtually all the votes counted, Clinton won a majority; Tsongas had one-third of the vote, and Brown had about one-tenth.

In both counties, Clinton spent months building support, particularly among retiree voters.

Tsongas, however, refused to look on Tuesday`s results as a defeat.

``The message is working,`` he told supporters at a rally in Massachusetts, where he won the primary. ``I`m still here.``

The Republican race was far quieter. To them, the results are a mere echo to primaries elsewhere. Buchanan was able to garner the one-third protest vote that he has consistently gotten. But he was not able to break through.

But then Buchanan did not really try.

Bush built upon his close friendships with most of the state`s Republican leaders. His son Jeb -- a former Florida secretary of state -- headed the Bush organization.

And Buchanan was hampered by something else -- his strong stand against further immigration to the United States. The position is a tough sell among Florida`s Hispanics, many of them first-generation emigres.

Buchanan made a token campaign stop in the state in early March, then all but ignored the state. Instead, he poured his energy and money into three other Super Tuesday states -- Louisiana and Mississippi, where he hoped a vast pool of conservative voters could carry him to upset victory, and Massachusetts, where he hoped to capitalize on a sour economy.

BROWARD QUOTES

What Broward County voters are saying about the presidential primaries.

He did not vote in the presidential race. ``I`m waiting to see what happens come November. ... It`s pretty tough out there. Even a blind man can see that.``